AD 2021-10-06 Airworthiness Directives; CFM International, S.A. Turbofan Engines

This AD applies to CFM International S.A. (CFM) LEAP-1B21, -1B23, -1B25, -1B27, -1B28, -1B28B1, -1B28B2, -1B28B3, -1B28B2C, -1B28BBJ1, and -1B28BBJ2 model turbofan engines with a pressure sub-system (PSS) unit with a serial number (S/N) listed in Additional Information, Paragraph 6.A. Table 1 of CFM Service Bulletin (SB) LEAP-1B-73-00-0038-01A-930A-D, Issue 002-00, dated 2021-04-25 (SB LEAP-1B-73-0038), installed.

Comply with this AD within the compliance times specified, unless already done.

(1) For an engine in service on the effective date of this AD that has accumulated fewer than 15 hours of electrical power applied to the PSS unit within the past 90 days, perform one of the following actions: (i) Prior to each flight, perform a check for the engine maintenance messages listed in the Accomplishment Instructions, paragraph 5.B.(2)(a) 2, of SB LEAP-1B-73-0038, related to the pressure transducer, until the PSS unit has accumulated 15 hours or more of electrical power within the previous 90 days; or (ii) Before further flight, apply electrical power to the PSS unit in accordance with the Accomplishment Instructions, paragraph 5.A.(3)(a) 1, of SB LEAP-1B-73-0038, until the PSS unit has accumulated 15 hours or more of electrical power within the past 90 days. (2) For an engine in service on the effective date of this AD that has accumulated 15 hours or more of electrical power applied to the PSS unit within the previous 90 days, within 5 flight cycles of the effective date of this AD, perform a one-time check for the maintenance messages listed in the Accomplishment Instructions, paragraph 5.B.(2)(a) 2, of SB LEAP-1B-73-0038, related to the pressure transducer. (3) For an engine not in service on the effective date of this AD that has accumulated fewer than 15 hours of electrical power applied to the PSS unit within the past 90 days, before further flight, apply electrical power to the PSS unit in accordance with the Accomplishment Instructions, paragraph 5.A.(3)(a) 1, of SB LEAP-1B-73-0038, until the PSS unit has accumulated 15 hours or more of electrical power within the previous 90 days. (4) For an engine not in service on the effective date of this AD that has accumulated 15 hours or more of electrical power applied to the PSS unit within the previous 90 days, before further flight, perform a check for the engine maintenance messages using the Accomplishment Instructions, paragraphs 5.A.(3)(b)1 through 5, of SB LEAP-1B-73-0038, related to the pressure transducer. (5) After accumulating 15 hours of electrical power on the PSS unit as required by paragraph (g)(1)(ii) or (g)(3) of this AD, before further flight, perform a check for the engine maintenance messages using the Accomplishment Instructions, paragraphs 5.A.(3)(b) 1 through 5, of SB LEAP-1B-73-0038, related to the pressure transducer. (6) If any engine maintenance messages are found by the checks required by paragraph (g)(1)(i), (2), (4), or (5) of this AD, before further flight, replace the PSS unit with a PSS unit eligible for installation.

This AD was prompted by multiple reports of PSS unit faults due to pressure transducer corrosion following extended storage periods. The FAA is issuing this AD to prevent erroneous pressure sensor signals that can impact engine thrust control. The unsafe condition, if not addressed, could result in loss of engine thrust control and reduced control of the airplane.

None.